Cloned pigs aren't identical

Cloned piglets vary as much as those from a naturally bred litter, according to a new US study. The researchers, based at the North Carolina State University and Texas A & M University, found that the amount of variation in appearance, physiology and behaviour within a cloned litter can even exceed that found in a normally produced litter. Their findings, which show that environmental factors have a strong influence on many physical characteristics, are published in the journals Applied Animal Behaviour Science, and Biology of Reproduction.

The scientists created two litters of cloned pigs, one of four piglets and one of five, and raised them alongside two litters of four naturally bred pigs. They found that traits such as body size, skin thickness, temper and blood sugar levels varied just as much in the cloned litters as in the naturally bred pigs. Their results confirm those of other studies, which indicate that genetically identical clones often differ physically. 'It is really clear that genes are not the whole picture, that some environmental levels are so strong you cannot control them even if you try' said study leader Jorge Piedrahita. He said that the environment in the womb was 'very, very important for the future behaviour and development of animals'.

Richard Gardner, chairman of the Royal Society's working group on cloning, said the study 'certainly shows that those who want to clone to replace a dead child have hugely unrealistic expectations'.